Tortugas Neuroscience Reports Positive Phase 2b Schizophrenia Results

FRAMINGHAM, Massachusetts — October 12, 2026

Phase 2b Trial Meets Primary Endpoint With Significant Symptom Improvement

The randomized, double-blind, placebo- and active-reference-controlled Phase 2b trial enrolled 363 Chinese adults with acute schizophrenia across 24 clinical centers. Participants were assigned to one of five groups: three obuprazine dose ranges of 1.5–3.0 mg, 4.5–6.0 mg and 6.0–9.0 mg, an aripiprazole reference group, or placebo. The primary endpoint was the change from baseline in PANSS total score at Day 42. The 1.5–3.0 mg dose group recorded a least-squares mean change of −28.6 points, compared with −11.9 points for placebo, representing a placebo-adjusted difference of −16.7 points (p<0.0001). The 4.5–6.0 mg and 6.0–9.0 mg groups demonstrated placebo-adjusted differences of −13.2 and −14.7 points, respectively, with both comparisons achieving p<0.0001. These findings indicate statistically significant improvements in overall schizophrenia symptom severity across all three tested dose ranges. The study also reported that the lower and middle dose groups showed higher PANSS responder rates, defined as at least a 50% reduction from baseline, compared with placebo and aripiprazole as early as Day 14.

Improvements Extend Across Positive, Negative and Cognitive Symptoms

Beyond the primary endpoint, the trial reported statistically significant and clinically meaningful improvements across several symptom domains at Day 42. All three obuprazine dose groups demonstrated benefits versus placebo on the PANSS positive symptom subscale, negative symptom subscale and Marder cognitive factor. In the 1.5–3.0 mg group, placebo-adjusted improvements were 5.3 points for positive symptoms and 4.4 points for negative symptoms, with both comparisons achieving p<0.0001. Positive symptoms can include hallucinations and delusions, while negative symptoms may involve reduced motivation, diminished emotional expression and social withdrawal. Cognitive-related difficulties can also affect everyday functioning in people with schizophrenia. The company additionally reported numerically greater efficacy for obuprazine than aripiprazole across multiple endpoints, including the primary endpoint; however, numerical differences alone do not establish statistical superiority over the active comparator. The results suggest that obuprazine may warrant further investigation as a treatment designed to address multiple symptom domains. Full trial data and peer-reviewed publication will be important for evaluating the clinical relevance, durability and consistency of these findings.

Obuprazine Safety Profile and Next Development Steps

Obuprazine was generally well tolerated during the Phase 2b trial. Discontinuation rates due to adverse events were approximately 2.1% among obuprazine-treated participants, compared with 2.5% in the placebo group. Detailed safety findings will be needed to provide a comprehensive assessment of adverse events and the candidate’s overall benefit-risk profile. Obuprazine has a pharmacological profile involving partial agonism at dopamine D2 and D3 receptors, antagonism of serotonin 5-HT2A receptors, and partial agonism at 5-HT1A receptors. These mechanisms are being investigated for their potential to support broad symptom control while maintaining tolerability. Tortugas Neuroscience holds global commercial development rights outside Greater China, while Hansoh Pharma has conducted multiple clinical trials of the candidate. Following the Phase 2b results, Tortugas plans to submit a U.S. IND application and expects detailed study findings to be submitted for publication in a peer-reviewed journal. Although the results represent an encouraging development milestone, obuprazine remains investigational, and additional clinical evaluation and regulatory review will be required to determine its safety and efficacy for schizophrenia.

Source::Tortugas Neuroscience, press release